In manufacturing capacitive pressure transducers, it is sometimes necessary to provide conductive through-hole metallization in holes in an insulating substrate. This necessitates providing a relatively thick layer of conductive metallization onto to a top surface of the substrate such that the metallization will also be provided in through holes therein. U.S. Pat. No. 4,384,899 illustrates such a capacitive pressure transducer utilizing a glass base substrate and conductive metallizations applied thereto to provide through-hole conductive paths. The pressure transducer illustrated in this patent comprises a silicon diaphragm forming one capacitive electrode which cooperates with another capacitive electrode comprising a metallization on a surface of a glass base substrate. In response to sensed pressure, the silicon diaphragm deflects and charges the capacitance between the diaphragm and the metallized glass base substrate.
In substrate metallization systems such as that discussed above, typically it is also necessary to solder to the metallization applied to the base substrate. Typically, the solder thermal coefficient of expansion is vastly dissimilar from the glass base substrate, and reliability problems are encountered due to the transmission of stress from the solder through the metallization to the metallization and glass base substrate interface. This problem becomes more severe when a relatively thick metallization layer is applied to the substrate, such as when feed through holes in the substrate are to be metallized. When solder is then applied to such a thick metallization layer, the result is often the eventual rupturing of the bond between the metallization and the insulating substrate or rupturing of the insulating substrate.